Dual chamber pacemaker therapy for mid-cavity obstructive hypertrophic cardiomyopathy.

Intracavitary LV obstruction is an important determinant of clinical outcome in hypertrophic cardiomyopathy (HCM). In a minority of patients the obstruction is at the level of the papillary muscles. Mid-cavity obstructive HCM may be associated with a distal LV aneurysm and a worse prognosis. It is often not amenable to standard cardiac surgeryfor LV outflow obstruction. The long-term effects (mean follow-up 4.8+/-2.9 years) of dual chamber (DDD) pacemaker therapy in 14 patients with mid-cavity obstructive HCM (mean age 34+/-16 years, range 15-65 years) were studied. Patients were evaluated by cardiac catheterization at baseline and 6 months to 1 year after receiving DDD pacemakers off all drug therapy. Symptoms were improved in all patients and NYHA functional class reduced from 2.8+/-0.1 to 1.9+/-0.4 (P < 0.0005). Intracavitary LV pressure gradients was reduced significantly (43+/-36 vs 84+/-31 mmHg at baseline, P < 0.0005). There was a significant associated reduction in apical LV systolic pressure (152+/-37 vs 188+/-34 mmHg, P < 0.001). In addition, there was a trend towards increased exercise tolerance (445+/-123 vs 396+/-165). Cardiac output and LV filling pressures were unchanged. In conclusion, chronic DDD pacing results in significant symptomatic and hemodynamic improvement in this uncommon but important subset of patients with obstructive HCM in whom the role of cardiac surgery is less well defined compared with the more typical outflow tract location of LV obstruction.